A laser pointer at 2B FPS [video]

As I understand it, this is sort of simulating what it would be like to capture this, by recreating the laser pulse and capturing different phases of it each time, then assembling them; so what is represented in the final composite is not a single pulse of the laser beam.

Would an upgraded version of this that was actually capable of capturing the progress of a single laser pulse through the smoke be a way of getting around the one-way speed of light limitation [0]? It seems like if you could measure the pulse's propagation in one direction, and the other (as measured by when it scatters of the smoke at various positions in both directions), this seems like it would get around it?

But it's been a while since I read an explanation for why we have the one-way limitation in the first place, so I could be forgetting something.

[0] https://en.wikipedia.org/wiki/One-way_speed_of_light

>As I understand it, this is sort of simulating what it would be like to capture this, by recreating the laser pulse and capturing different phases of it each time, then assembling them; so what is represented in the final composite is not a single pulse of the laser beam.

It is not different phases, but it is a composite! On his second channel he describes the process[0]. Basically, it's a photomultiplier tube (PMT) attached to a precise motion control rig and a 2B sample/second oscilloscope. So he ends up capturing the actual signal from the PMT over that timespan at a resolution of 2B samples/s, and then repeating the experiment for the next pixel over. Then after some DSP and mosaicing, you get the video.

>It seems like if you could measure the pulse's propagation in one direction, and the other (as measured by when it scatters of the smoke at various positions in both directions), this seems like it would get around it?

The point here isn't to measure the speed of light, and my general response when someone asks "can I get around physics with this trick" by answer is no. But I'd be lying if I said I totally understood your question.

[0] https://www.youtube.com/watch?v=-KOFbvW2A-o

No, you cannot escape the conclusion of the limitations on measuring the one-way speed of light.

While the video doesn't touch on this explicitly, the discussion of the different path lengths around 25:00 in is about the trigonometric effect of the different distances of the beam from the camera. Needing to worry about that is the same grappling with the limitation on the one-way speed.

Think of it more like "IRL raytracing", where a ray (the beam) is cast and the result for a single pixel from the point of view is captured, and then it is repeated millions of times.

Even if you had a clock and camera for every pixel, the sync is dependent on the path of the signal taken. Even if you sent a signal along every possible route and had a clock for each route for each pixel (a dizzingly large number) it still isn't clear that this would represent a single inertial frame. As I understand it even if you used quantum entanglement for sync, the path of the measurement would still be an issue. I suggest not thinking about this at all, it seems like an effective way to go mad https://arxiv.org/pdf/gr-qc/0202031

E: Do not trust my math under any circumstances but I believe the number of signal paths would be something like 10^873,555? That's a disgustingly large number. This would reveal whether the system is in a single inertial frame (consistency around loops), but it does not automatically imply a single inertial frame. It's easy to forget that the earth, galaxy, etc are also still rotating while this happens.

The problem (ignoring quantum mechanics) is that the sensors all require an EM field to operate in. So assuming that the speed of light was weighted with a vector in space-time, it would be affected everywhere -- including in the measurement apparatus.

If on the other hand one could detect a photon by sending out a different field, maybe a gravitational wave instead... well it might work, but the gravitational wave might be affected in exactly the same way that the EM field is affected.

No, as he explains in the video, this is not a stroboscopic technique, the camera _does_ capture at 2 billion fps. But it is only a single pixel! He actually scans the scene horizontally then vertically and sends a pulse then captures pixel by pixel.